Method for depositing a gap-fill layer by plasma-assisted deposition

ABSTRACT

A film having filling capability of a patterned recess on a surface of a substrate is deposited by forming a viscous material in a gas phase by striking a plasma in a chamber filled with a volatile precursor that can be polymerized within certain parameter ranges which include a partial pressure of the precursor during a plasma strike and substrate temperature.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of, and claims priority to, U.S. patent application Ser. No. 16/962,841 filed Jul. 16, 2020 titled METHOD FOR DEPOSITING A GAP-FILL LAYER BY PLASMA-ASSISTED DEPOSITION; which is a 371 of International Application No. PCT/IB2019/000084 filed Jan. 18, 2019 titled METHOD FOR DEPOSITING A GAP-FILL LAYER BY PLASMA-ASSISTED DEPOSITION filed Jan. 18, 2019; which claims the benefit of U.S. Provisional Application No. 62/619,569 filed Jan. 19, 2018 titled METHOD FOR DEPOSITING A GAP-FILL LAYER CONTAINING SILICON AND CARBON BY PLASMA-ASSISTED DEPOSITION, the disclosures of which including any appendices, are incorporated herein by reference to the extent such disclosures do not conflict with the present disclosure.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention generally relates to a method for depositing a gap-fill layer in trenches by plasma-assisted deposition.

Description of the Related Art

In processes of fabricating integrated circuits such as those for shallow trench isolation, inter-metal dielectric layers, passivation layers, etc., it is often desirable to fill trenches (any recess typically having an aspect ratio of one or higher) with insulating material. However, with miniaturization of wiring pitch of large scale integration (LSI) devices, void-free filling of high aspect ratio spaces (e.g., AR≥3) becomes increasingly difficult due to limitations of existing deposition processes.

FIG. 2 illustrates schematic cross sectional views of trenches subjected to a conventional plasma-enhanced CVD process for gap filling in the order of (a) and (b). In the conventional plasma-enhanced CVD process, since plasma reaction occurs in a gas phase and reaction products accumulate on a surface of a substrate, film growth is faster at the top of a trench 103 of a substrate 101 than inside the trench 103. As a result, when a layer 102 is deposited, an overhang part 104 is necessarily formed as illustrated in (a). Further, since in the conventional CVD process, deposition is performed layer by layer, when a next layer 105 is deposited on the layer 102, the upper opening of the trench 103 is closed, leaving a void 106 inside the trench 103 as illustrated in (b).

FIG. 3 illustrates schematic cross sectional views of trenches subjected to a conventional gap-fill process in the order of (a), (b), and (c) using an inhibitor. By depositing an inhibitor 202 in a trench 201, which inhibits reaction products from accumulating on a surface that is covered with the inhibitor, as illustrated in (b), the reaction products do not accumulate on the top surface and at the top of the trench 201, while accumulating at the bottom of the trench 201, achieving bottom-up fill 203 as illustrated in (c). However, it is difficult to find suitable combinations of an inhibitor and an activator, and find suitable process conditions for deposition. In many cases, such a process is not practical.

FIG. 4 illustrates schematic cross sectional views of trenches subjected to a conventional gap-fill process in the order of (a) and (b) using a highly anisotropic process. The high anisotropic process is typically an ion driven deposition wherein ion bombardment by a plasma containing ions causes plasma reaction for depositing a layer, thereby anisotropically depositing a layer 302 on a top surface and a layer 303 inside a trench 301 as bottom-up fill, as illustrated in (b). However, when the trench is deeper, in order to bombard a bottom area of the trench with ions, the mean free path of ions has to made longer to reach the bottom area by, e.g., significantly reducing pressure to a hard vacuum, which is often costly and unpractical.

FIG. 5 illustrates schematic cross sectional views of trenches subjected to a conventional gap-fill process in the order of (a) and (b) or (c) and (d) using a volume expansion treatment ((d) shows loading effect). After depositing a layer 402 on a surface of a substrate 405 having a trench 401 as illustrated in (a), by, e.g., oxidizing the layer, the layer can be expanded, thereby increasing the volume or thickness of the layer and closing the gap (trench) 401 as illustrated in (b). However, as illustrated in (c), when trenches consist of a narrow trench 401 and a wide trench 403, due to the loading effect (i.e., a variation of filling speed depending on the density of a pattern is called the “loading effect”), even when the narrow trench is closed, the wide trench still has a significant opening 404 as illustrated in (d). Also, when the layer is expanded and closes the trench, the layers facing each other push against each other, thereby exerting stress on the sidewalls of the trench as indicated in (d) by arrows, which often causes the structure of the trench to partially or significantly collapse.

FIG. 6 shows STEM photographs of cross-sectional views of trenches subjected to a conventional gap-fill process using a combination of deposition in (a), dry-etching in (b) to (d) using different etchants, and 2^(nd) deposition in (e) to (g) corresponding to (b) to (d), respectively. By combing deposition and etching, the topology or geometry of a gap-filled trench can be adjusted. However, as shown in FIG. 6 , regardless of the type of etchant (CF₄ in (b) and (e), CHF₃ in (c) and (f), and C₄F₈ in (d) and (g)), the initial voids in the narrow trenches were not filled by etching and subsequent deposition. Further, as shown in FIG. 6 , the loading effect manifested. Additionally, this process is time consuming since at least deposition is repeated and therebetween etching is performed.

FIG. 7 illustrates schematic cross sectional views of trenches subjected to a conventional gap-fill process in the order of (a) and (b) using a flowable material. Since liquid or viscous gas is flowable and naturally moves to the bottom of a trench, by using such liquid or viscous gas, a trench 502 formed in a substrate 501 can be filled with the flowable material, forming bottom-up fill 503 as illustrated in (b). Normally, in order to keep the material flowable, the temperature of the substrate is kept at a low temperature such as 50° C. or lower. This process is very fast and efficient. Although the loading effect is manifested, that is not normally a problem because all the trenches can be overfilled, followed by CMP. However, the material is typically of very poor quality and requires an additional curing step. Further, when the trench is narrow, surface tension of the flowable material interferes with or even blocks entry of the flowable material into the inside of the trench. FIG. 8 illustrates a schematic cross sectional view of trenches subjected to a conventional gap-fill process using a flowable material and shows the above problem. In this process, a flowable state of a precursor is achieved by polymerization in a reaction chamber which occurs when mixing with another precursor in a gas phase above a substrate, i.e., before reaching the surface of the substrate and/or immediately after contacting the top surface of the substrate. By polymerization with the other precursor in the gas phase, the precursor immediately changes to a flowable state before reaching the surface of the substrate and/or at the moment of contacting the top surface of the substrate when its temperature is kept at very low temperature. In any case, the flowable state is achieved always before entering into the trench. As a result, as illustrated in FIG. 8 , the flowable material 504 does not enter the trench 502 of the substrate 501, and due to the surface tension of the flowable material 504, the top opening of the trench 502 is clogged by a lump 505 and entry of the flowable material 504 into the trench 502 is blocked. Additionally, in order to form a flowable state of a precursor, the process always uses oxygen and nitrogen, sometimes hydrogen chemistry, and/or the precursor must have very low vapor pressure.

Any discussion of problems and solutions involved in the related art has been included in this disclosure solely for the purposes of providing a context for the present invention and should not be taken as an admission that any or all of the discussion were known at the time the invention was made.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present disclosure provide gap filling methods that include plasma-assisted deposition. As set forth in more detail below, recesses or gaps on a substrate surface can be filled substantially without formation of voids and/or under conditions where a nitrogen, oxygen, or hydrogen plasma is not required. Various embodiments can solve one or more of the above-discussed problems.

An object of the present invention in some embodiments is to provide a film having filling capability. In some embodiments, the filling capability can be accomplished by forming a viscous material in a gas phase by striking, for example, an Ar and/or He plasma in a chamber filled with a volatile precursor that can be polymerized within certain parameter ranges. The parameters can include, for example, partial pressure of precursor during a plasma strike and wafer temperature. As used herein, polymerization can include formation of a longer molecule and need not necessarily include a carbon-carbon bond. The viscous phase flows at a bottom of a trench and fills the trench with a film having bottom up seamless material. In some embodiments, this process can be demonstrated using tetramethysilane and/or dimethyldivinylsilane (DMDVS) as a precursor; however, many other alkylsilane compounds or other compounds can be used singly or in any combination. In some embodiments, the processes use exclusively a silicon or silicon-carbon precursor, and an inert gas to strike a plasma. In some embodiments, the processes use ALD-like recipes (e.g., feed/purge/plasma strike/purge), wherein the purge after feed is voluntarily severely shortened, compared to traditional ALD processes, to leave high partial pressure of precursor during the plasma strike. This is clearly distinguished from typical ALD chemistry or mechanism.

The above processes can be based on pure CVD and pulse plasma CVD which also impart good filling capabilities to resultant films, although the ALD-like recipes may be more beneficial as discussed later.

In some embodiments, the desired aspects for flowability of depositing film include:

1) High enough partial pressure during the entire RF-ON period for polymerization/chain growth to progress;

2) Sufficient energy to activate the reaction (defined by the RF-ON period and RF power), not too long RF-ON period; and

3) Temperature and pressure for polymerization/chain growth set above a melting point of flowable phase but below a boiling point of the deposited material.

In some embodiments, a silicon (e.g., a Si— and C—) containing layer is converted to a SiO-based layer by post deposition oxygen plasma treatment.

For purposes of summarizing aspects of the invention and the advantages achieved over the related art, certain objects and advantages of the invention are described in this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

Further aspects, features and advantages of this invention will become apparent from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will now be described with reference to the drawings of preferred embodiments which are intended to illustrate and not to limit the invention. The drawings are greatly simplified for illustrative purposes and are not necessarily to scale.

FIG. 1A is a schematic representation of a PEALD (plasma-enhanced atomic layer deposition) apparatus suitable for depositing a film in accordance with at least one embodiment of the present disclosure.

FIG. 1B illustrates a schematic representation of a precursor supply system using a flow-pass system (FPS) usable in accordance with at least one embodiment of the present disclosure.

FIG. 2 illustrates schematic cross sectional views of trenches subjected to a conventional CVD process for gap filling in the order of (a) and (b).

FIG. 3 illustrates schematic cross sectional views of trenches subjected to a conventional gap-fill process in the order of (a), (b), and (c) using an inhibitor.

FIG. 4 illustrates schematic cross sectional views of trenches subjected to a conventional gap-fill process in the order of (a) and (b) using a highly anisotropic process.

FIG. 5 illustrates schematic cross-sectional views of trenches subjected to a conventional gap-fill process in the order of (a) and (b) or (c) and (d) using a volume expansion treatment ((d) shows loading effect).

FIG. 6 shows scanning transmission electron microscope (STEM) photographs of cross-sectional views of trenches subjected to a conventional gap-fill process using a combination of deposition in (a), dry-etching in (b) to (d) using different etchants, and 2^(nd) deposition in (e) to (g) corresponding to (b) to (d), respectively.

FIG. 7 illustrates schematic cross sectional views of trenches subjected to a conventional gap-fill process in the order of (a) and (b) using a flowable material.

FIG. 8 illustrates a schematic cross sectional view of trenches subjected to a conventional gap-fill process using a flowable material.

FIG. 9 illustrates schematic cross sectional views of trenches subjected to a gap-fill process in the order of (a), (b), and (c) according to an embodiment of the present invention.

FIG. 10 shows STEM photographs of cross-sectional views of narrow trenches subjected to gap-fill cycles repeated 50 times in (a) and 250 times in (c), and wide trenches subjected to gap-fill cycles repeated 50 times in (b) and 250 times in (d) according to an embodiment of the present invention.

FIG. 11 shows STEM photographs of cross-sectional views of wide trenches subjected to gap-fill cycles in (a), and narrow trenches subjected to gap-fill cycles in (b) according to an embodiment of the present invention.

FIG. 12 shows Fourier Transform Infrared (FTIR) spectra of a gap-fill layer according to an embodiment of the present invention.

FIG. 13 shows STEM photographs of cross-sectional views of gap-filled wide trenches subjected to periodic hydrogen plasma treatment in (a), and gap-filled narrow trenches subjected to periodic hydrogen plasma treatment in (b) according to an embodiment of the present invention.

FIG. 14 shows STEM photographs of cross-sectional views of narrow trenches subjected to gap-fill cycles repeated 50 times in (a) and 250 times in (c), and wide trenches subjected to gap-fill cycles repeated 50 times in (b) and 250 times in (d) according to an embodiment of the present invention.

FIG. 15 shows graphs indicating the schematic relationship between process parameters and flowability according to embodiments of the present invention.

FIG. 16 shows a STEM photograph of a cross-sectional view of wide and narrow trenches subjected to gap-fill deposition by pure PECVD according to an embodiment of the present invention.

FIG. 17 shows a STEM photograph of a cross-sectional view of wide and narrow trenches subjected to gap-fill deposition by pulse feed PECVD according to a comparison example.

FIG. 18 shows a STEM photograph of a cross-sectional view of wide and narrow trenches subjected to gap-fill deposition by pulse plasma PECVD according to an embodiment of the present invention.

FIG. 19 shows STEM photographs of cross-sectional views of gap-filled trenches using, as dry gas, 100% He in (a), 80% He+20% H₂ in (b), 80% He+20% N₂ in (c), 80% He+20% Ar in (d), and 80% He+20% O₂ in (e) according to embodiments of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

In this disclosure, “gas” may include vaporized solid and/or liquid and may be constituted by a single gas or a mixture of gases, depending on the context. Likewise, an article “a” or “an” refers to a species or a genus including multiple species, depending on the context. In this disclosure, a process gas introduced to a reaction chamber through, for example, a showerhead may be comprised of, consist essentially of, or consist of a precursor and an additive gas. The additive gas may include a reactant gas for, for example, nitriding and/or carbonizing the precursor, and an inert gas (e.g., noble gas) for exciting the precursor, when RF power is applied to the additive gas. The inert gas may be fed to a reaction chamber as a carrier gas and/or a dilution gas. In accordance with examples of this disclosure, no reactant gas for oxidizing the precursor is necessarily used. Further, in some embodiments, no reactant gas is used, and only noble gas (as a carrier gas and/or a dilution gas) is used. The precursor and the additive gas can be introduced as a mixed gas or separately to a reaction space. The precursor can be introduced with a carrier gas such as a rare gas. A gas other than the process gas, i.e., a gas introduced without passing through the showerhead, other gas distribution device, or the like, may be used for, e.g., sealing the reaction space, which includes a seal gas such as a rare gas. In some embodiments, the term “precursor” refers generally to a compound that participates in the chemical reaction that produces another compound, and particularly to a compound that constitutes a film matrix or a main skeleton of a film, whereas the term “reactant” refers to a compound, other than precursors, that activates a precursor, modifies a precursor, or catalyzes a reaction of a precursor, wherein the reactant may provide an element (such as N, C) to a film matrix and become a part of the film matrix, when RF power is applied. The term “inert gas” refers to a gas that excites a precursor when RF power is applied, but unlike a reactant, it does not become a part of a film matrix to an appreciable extent.

In some embodiments, “film” refers to a layer continuously extending in a direction perpendicular to a thickness direction substantially without pinholes to cover an entire target or concerned surface, or simply a layer covering a target or concerned surface. In some embodiments, “layer” refers to a structure having a certain thickness formed on a surface or a synonym of film or a non-film structure. A film or layer may be constituted by a discrete single film or layer having certain characteristics or multiple films or layers, and a boundary between adjacent films or layers may or may not be clear and may or may not be established based on physical, chemical, and/or any other characteristics, formation processes or sequence, and/or functions or purposes of the adjacent films or layers. Further, in this disclosure, any two numbers of a variable can constitute a workable range of the variable as the workable range can be determined based on routine work, and any ranges indicated may include or exclude the endpoints. Additionally, any values of variables indicated (regardless of whether they are indicated with “about” or not) may refer to precise values or approximate values and include equivalents, and may refer to average, median, representative, majority, etc. in some embodiments. Further, in this disclosure, the terms “constituted by” and “having” refer independently to “typically or broadly comprising,” “comprising,” “consisting essentially of,” or “consisting of” in some embodiments. In this disclosure, any defined meanings do not necessarily exclude ordinary and customary meanings in some embodiments.

In this disclosure, “continuously” refers to without breaking a vacuum, without interruption as a timeline, without any material intervening step, without changing treatment conditions, immediately thereafter, as a next step, or without an intervening discrete physical or chemical structure between two structures other than the two structures in some embodiments.

In this disclosure, the term “filling capability” refers to a capability of filling a gap substantially without voids (e.g., no void having a size of approximately 5 nm or greater in diameter) and seams (e.g., no seam having a length of approximately 5 nm or greater), wherein seamless/void less bottom-up growth of a layer is observed, which growth at a bottom of a gap is at least approximately 1.5 times faster than growth on sidewalls of the gap and on a top surface having the gap. A film having filling capability is referred to also as “flowable film” or “viscous film.” The flowable or viscous behavior of a film is often manifested as a concave surface at a bottom of a trench. For example, FIG. 11 shows STEM photographs of cross-sectional views of wide trenches subjected to gap-fill cycles in (a), and narrow trenches subjected to gap-fill cycles in (b) according to an embodiment of the present invention. As shown in (a) and (b) of FIG. 11 , the flowable film shows growth at the bottom of the trenches which is at least approximately 1.5 times faster than growth on the sidewalls of the trenches and on the top surface. In contrast, FIG. 14 shows STEM photographs of cross-sectional views of narrow trenches in (a) and wide trenches in (b) in which a film without filling capability is deposited (using the same precursor as in FIG. 11 ). As shown in FIG. 14 , the non-flowable film shows growth at the bottom of the trenches which is approximately the same as growth on the top surface, and does not manifest a substantially concave surface at the bottom.

In the above, the “growth” rate defined by a thickness drops once the trench is filled; however, since this is a flowable process, a volumetric growth should be considered. Typically, the growth per nm³ is constant throughout the deposition step, although the narrower the trench, the faster in the Z (vertical) direction the growth becomes. Further, since the precursor flows to the bottom of a recess, once all the trench, holes, or other recesses are filled, regardless of the geometry, the growth proceeds in a classical manner by planarization effect, forming a substantially planar surface as shown in FIG. 13 . FIG. 13 shows STEM photographs of cross-sectional views of gap-filled wide trenches in (a), and gap-filled deep, narrow trenches in (b) according to an embodiment of the present invention. In some embodiments, the growth rate of flowable film in a traditional sense is in a range of 0.01 to 10 nm/cycle on a planar surface (as blanket deposition)

In this disclosure, a recess between adjacent protruding structures and any other recess pattern are referred to as a “trench.” That is, a trench is any recess pattern including a hole/via and which can have, in some embodiments, a width of about 20 nm to about 100 nm (typically about 30 nm to about 50 nm) (wherein when the trench has a length substantially the same as the width, it can be referred to as a hole/via, and a diameter thereof can be about 20 nm to about 100 nm), a depth of about 30 nm to about 100 nm (typically about 40 nm to about 60 nm), and an aspect ratio of about 2 to about 10 (typically about 2 to about 5). The dimensions of the trench may vary depending on the process conditions, film compositions, intended applications, etc.

Flowability of film is temporarily obtained when a volatile precursor, for example an alkylsilane or the like, is polymerized by a plasma and deposited on a surface of a substrate, wherein gaseous precursor (e.g., monomer) is activated or fragmented by energy provided by plasma gas discharge so as to initiate polymerization, and when the resultant material is deposited on the surface of the substrate, the material shows temporarily flowable behavior. In accordance with exemplary embodiments, when the deposition step is complete, the flowable film is no longer flowable but is solidified, and thus, a separate solidification process is not required.

Since typically, plasma chemistry is very complex, and the exact nature of the plasma reaction is hard to characterize and largely unknown, it can be difficult to illustrate a reaction formula when a precursor is polymerized. However, without restricting the present invention, the following reaction (since plasma polymerization is complex, the formula does not represent stoichiometrically accurate reaction) may take place when alkylsilane is polymerized by a plasma, forming viscous/flowable material:

Deposition of some flowable films is known in the art; however, conventional deposition of a flowable film requires a precursor having two silicon atoms, makes no mention of polymer formation, specifies hydrogen as a required reactant, involves at least one of N-containing chemistry, O-containing chemistry, and H-containing chemistry, and forms a target material, which is not SiC. In contrast, in some embodiments, none of N-containing chemistry, O-containing chemistry, and/or H-containing chemistry is required, no limitation is imposed on the number of silicon atoms included in a precursor, and various specific examples can involve Si—C chemistry, forming a Si—C polymer (which excludes, in some embodiments, materials constituted substantially or predominantly by SiO(CN), SiO(N), SiNH(OC), SiOCN, SiO(CN), SiCN(O), SiNO, SiO, SiN, SiOCH, SiCN, SiCO, SiN(C), and C). In some embodiments, flowable film is constituted by neither polysiloxane nor polysilazane, and although any suitable one or more of precursors (for example, each containing a Si—C bond) can be used as a precursor, in some embodiments, alkoxysilane or aminosilane is not used as a precursor.

In some embodiments, a volatile precursor is polymerized within a certain parameter range mainly defined by partial pressure of precursor during a plasma strike, wafer temperature, and pressure in a reaction chamber. In order to adjust the “precursor partial pressure,” an indirect process knob (dilution gas flow) is often used to control the precursor partial pressure. The absolute number of precursor partial pressure may not be required in order to control flowability of deposition film, and instead, a ratio of flow rate of precursor to flow rate of the remaining gas and the total pressure in the reaction space at a reference temperature can be used as practical control parameters. If the precursor is very dilute, the chain growth stops before being able to manifest rich liquid-phase-like behavior, or polymerization may not occur at all as in standard plasma CVD deposition. If the precursor gas ratio is low during the entire period of plasma strike, no or little bottom-up fill is observed, assuming that the total pressure and the temperature are constant (this assumption is applied when the precursor gas ratio is discussed unless stated otherwise). At a low precursor gas ratio, polymerization may occur to a certain degree, but supply is too low to form polymer chains, which are long enough to have the liquid-like behavior. In some embodiments, the precursor gas ratio (a ratio of precursor flow rate to the total gas flow rate) is in a range of about 10% to about 100%, preferably about 50% to about 90%.

In some embodiments, such parameter ranges are adjusted as follows:

TABLE 1 (numbers are approximate) Low ← Viscosity → High Partial pressure of precursor >50 Preferably, >200 (Pa) Wafer temperature (° C.) −10 to 200 Preferably, 50 to 150 Total pressure (Pa)    300 to 101325 Preferably, >500

As for pressure, high pressure is preferable for flowability, since gravity is the driving force for the film to flow at the bottom of a trench. As for temperature, low temperature is preferable for flowability (this is much less intuitive), although high temperature favors the polymer chain growth rate. For example, the phase change between gas precursor and solidification may be as follows:

TABLE 2 Chain length x 5x 10x State gas liquid Solid

Alternatively or additionally, the solidification may occur upon contact with a substrate wherein this reaction is activated thermally. As for precursor gas ratio, a high precursor gas ratio is preferable for flowability, since under a low precursor partial pressure, although polymerization may occur, supply is too low to form polymer chains, which are long enough to have the liquid-like behavior. As for RF-on time, there is an optimum for RF-on time below or above which the ability to flow to the bottom is degraded (the optimum depends of the other process parameters). It should be noted that changing these process parameters can significantly change the bottom up growth process window. For example, when flowability of depositing film is observed at 50° C. and at a pressure 500 Pa, the pressure can be changed to at least 700 Pa at 75° C. while keeping all other parameters constant to maintain desired growth characteristics. The same is true for pressure, temperature, and precursor gas ratio.

FIG. 15 shows graphs indicating the schematic relationships between process parameters and flowability according to embodiments (PEALD-like process) of the present disclosure. The vertical axis (“top/bottom”) refers to a ratio of (top thickness in an isolated area)/(bottom thickness in an isolated area), wherein a ratio of 1 indicates that the depositing film has no flowability, whereas a ratio of 0 indicates that the depositing film has a full or complete flowability. For example, the top middle cell shows the relationship between temperature (deposition temperature) and flowability as a function of pressure (total pressure), wherein, for example, when the pressure is 800 Pa, the flowability is about 0.4 at a temperature of 125° C. and about 0.1 at a temperature of 75° C. Likewise, the top right cell shows the relationship between temperature (deposition temperature) and flowability as a function of dry He flow (wherein a precursor flows at 0.1 slm using a carrier gas), wherein, for example, when the dry He flow is 1.0 slm, the flowability is about 0.4 at a temperature of 125° C. and about 0.1 at a temperature of 75° C. The following table shows more examples:

TABLE 3 (numbers are approximate) Temp Pressure He flow Recipe [° C.] [Pa] [slm] T/B flowable 1 85 1100 0.5 0.12 Yes 2 85 1100 1 0.06 Yes 3 85 1100 1.5 0.17 Yes 4 85 800 1.5 0.24 Yes 5 85 500 0.5 0.17 Yes 6 85 500 1.305 0.65 Yes 7 120 1100 0.5 0.32 Yes 8 120 1100 1.5 0.30 Yes 9 120 800 1 0.39 Yes 10 120 500 0.5 0.43 Yes 11 120 500 1.5 0.92 Yes

In the above, “T/B” refers to a ratio of (top thickness in an isolated area)/(bottom thickness in an isolated area), and the common conditions were shown in Table 4 below. These are merely examples that are not intended to limit the present invention.

TABLE 4 (numbers are approximate) RF power 300 W Feed 0.1 sec. Purge 0.2 sec. RF 1 sec. Purge 0.5 sec. Gap between upper and lower electrodes 15 mm

All of Recipes 1 to 11 show the deposited film was flowable (a ratio of top/bottom is always less than 1), but the degree of flowability varied, i.e., the aim of these data is not to find the process window but to optimize performance. In view of FIG. 15 and Table 4, a skilled artisan in the art can readily understand that these show strong interaction of pressure and dry He flow as for flowability of depositing film. If the pressure is high, dry He flow has a limited impact on flowability, and if the pressure is low (e.g., 500 Pa), low dry He flow (high partial pressure of precursor) is desired to provide good flowability. As for temperature, there is no such interaction observed, and it just shifts performance as shown in FIG. 15 (shifting along the vertical axis indicated by parallel lines in FIG. 15 ). In the present disclosure, where conditions and/or structures are not specified, a skilled artisan in the art can readily provide such conditions and/or structures to optimize the process conditions, in view of the present disclosure in its entirety, as a matter of routine experimentation.

A flowable film can be deposited not only by plasma-enhanced atomic layer-like deposition (PEALD), but also by plasma-enhanced chemical vapor deposition (PECVD) with continuous plasma or pulsing plasma. However, typically, PECVD with pulsing feed (on-off pulse) is not preferable, since the precursor partial pressure becomes too low when no precursor is fed to a reaction space while RF power is applied to the reaction space. The precursor partial pressure at a reference temperature for depositing flowable film should be more than that for depositing non-flowable film, since a relatively high molar concentration of the precursor at a reference temperature is desired, while RF power is applied to cause plasma polymerization to render the depositing film flowable, with reference to conditions employed, when plasma reaction products are continuously formed in a gas phase by PECVD and are continuously deposited on a substrate wherein a void is formed in a trench as shown in FIG. 2 or conditions employed when plasma reaction products are formed only on a surface by surface reaction by PEALD, wherein a bottom-up structure cannot be formed in a trench. In some embodiments, in PEALD, by shortening a duration of purge so that a precursor on a top surface can be predominantly removed while a precursor in a trench can remain in the trench, and when the precursor is exposed to a plasma, more viscous material is formed in the trench than on the top surface, and also the viscous material flows toward the bottom of the trench, thereby forming a layer having a concave surface at the bottom. As discussed above, in PEALD, by substantially under dosing or shortening the purging after the precursor feed, the molar concentration of the precursor in the trench can remain relatively high at the reference temperature, when RF power is applied to the reaction space. In some embodiments, the purge after the precursor feed is so shortened that the precursor partial pressure at the reference temperature in the trench after the shortened purge may be considered to be substantially the same as the precursor partial pressure at the reference temperature when the precursor is fed to the reaction space. It should be noted that the above process is clearly different from conventional PEALD; however, for convenience, in this disclosure, the above process may be referred to as PEALD-like process or simply as PEALD, wherein PEALD refers to a process using an apparatus for PEALD.

In some embodiments, the duration (seconds) of purge after the precursor feed in an ALD cycle is 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0, and ranges between any two of the forgoing numbers, depending on the chamber volume, distance between upper and lower electrodes, feed time, purge time, total gas flow, vapor pressure of the precursor (the dose of which also depends on the ambient temperature and remaining precursor amount in a bottle, etc.), etc., which a skilled artisan in the art can determined through routine experimentations based on this disclosure in its entirety. In some embodiments, the flow rate (sccm) of precursor is 50, 100, 150, 200, 300, 400, 500, 600, 700, and ranges between any two of the forgoing numbers, in both PEALD-like process and PECVD with continuous or pulsing plasma, also depending on the above-described factors. In some embodiments, the duration of precursor feed is the duration (seconds) of precursor feed in an ALD cycle is 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0, and ranges between any two of the forgoing numbers, in PEALD-like process, also depending on the above-described factors. In some embodiments, the duration (seconds) of RF power application is 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0, and ranges between any two of the forgoing numbers, depending on the above-described factors. In some embodiments, the duration (seconds) of purge after RF power application is 0.0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0, and ranges between any two of the forgoing numbers, depending on the above-described factors.

FIG. 9 illustrates the above-discussed PEALD-like process, showing schematic cross sectional views of trenches subjected to a gap-fill process in the order of (a), (b), and (c) according to an embodiment of the present invention. A substrate 31 having trenches 32 is placed in a reaction space in (a), and a precursor is fed to the reaction space, thereby filling the trenches 32 with a gas phase precursor 33 in (b). Thereafter, the gas phase precursor is exposed to a plasma strike, thereby forming a viscous phase directly in the trenches 32 (not before as in standard PECVD, nor after as in standard PEALD), which deposits in the trenches 32 and also flows into the trenches 32, wherein a viscous matter (e.g., polymer) 36 is accumulated at the bottoms of the trenches 32 (the surface is schematically indicted as a planar surface for illustrative purposes), whereas little deposition 35 is observed on the sidewalls and merely a thin layer 34 is deposited on the top surface in (c). This plasma polymerization process does not require nitrogen, oxygen, or hydrogen as a reactant, or chamber pressure restriction.

Although flowable film can be deposited not only by PEALD-like process but also by PECVD with constant plasma or pulsing plasma, there may be a benefit using PEALD-like process. For example, it is beneficial when the precursor is switching from a gas phase to a liquid phase intermittently during the deposition, because a constant liquid phase would be more likely to have a surface tension problem (which is highly structure-dependent, and the narrower the trench, the worse the problem becomes) as shown in FIG. 8 . Further, PECVD with constant or pulsing plasma is evidently much more precursor-consuming than is PEALD-like process.

As described above, in order to realize flowability of precursor, the precursor partial pressure at a reference temperature in a reaction space may be one of the important parameters, since the molar concentration of the precursor can be expressed as follows:

n/V=p/RT (ideal gas law)

wherein T: thermodynamic temperature, P: pressure, n: amount of substance, V: volume, and R: gas constant.

Thus, if the temperature for deposition becomes higher, the precursor partial pressure for deposition should also become higher to maintain the same molar concentration. If the temperature is constant, the molar concentration of the precursor directly corresponds to the precursor partial pressure which can be treated as a controlling process parameter. Further, if a period of RF power application is prolonged in a PEALD-like process, the molar concentration of the precursor in the trenches decreases toward the end of the period, which can lead to an insufficient amount of precursor molecules in the trenches being exposed to a plasma, resulting in deposition of less or hardly flowable material, or solidifying already deposited flowable material, or stopping flowability of the material. If a period of RF power application is too short, on the other hand, sufficient plasma polymerization may not occur, and thus, flowable film may not be formed or deposited in the trenches. In some embodiments, the period of RF power application (the period of being exposed to a plasma) may be in a range of about 0.7 seconds to about 2.0 seconds (preferably about 1.0 seconds to about 2.0 seconds), which range can be applied to both PEALD-like process and PECVD with pulsing plasma. The plasma exposure time can also be adjusted by changing the distance between upper and lower electrodes (conductively coupled parallel electrodes) wherein by increasing the distance, the retention time in which the precursor is retained in the reaction space between the upper and lower electrodes can be prolonged when the flow rate of precursor entering into the reaction space is constant. In some embodiments, the distance (mm) between the upper and lower electrodes is 5, 10, 15, 20, 25, 30, and ranges between any two of the forgoing numbers. In some embodiments, RF power (W) (e.g., 13.56 MHz) for flowable film deposition is 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 10000, and ranges between any two of the forgoing numbers as measured for a 300-mm wafer which can be converted to units of W/cm² for different sizes of wafers, in both PEALD-like process and PECVD with continuous or pulsing plasma.

In the present disclosure where conditions and/or structures are not specified, the skilled artisan in the art can readily provide such conditions and/or structures, in view of the present disclosure, as a matter of routine experimentation.

In all of the disclosed embodiments, any element used in an embodiment can be replaced with any elements equivalent thereto, including those explicitly, necessarily, or inherently disclosed herein, for the intended purposes. Further, the present invention can equally be applied to apparatuses and methods.

The embodiments will be explained with respect to preferred embodiments. However, the present invention is not limited to the preferred embodiments.

Exemplary methods of filling a patterned recess or trench on a substrate include providing a substrate comprising the recess/trench in a reaction space, providing a precursor to the reaction space, thereby filling the recess with the precursor, and providing a plasma to form a viscous phase of the precursor in the recess, wherein the viscous phase of the precursor flows and deposits or forms deposited material in the bottom portion of the recess relative to sidewalls and/or a top portion of the substrate away from the recess.

Some embodiments provide a method for filling a patterned recess of a substrate by plasma-assisted deposition of a film having filling capability using a precursor in a reaction space, where a film without filling capability is depositable as a reference film on the substrate using the precursor in the reaction space when the precursor is supplied to the reaction space in a manner providing a first partial pressure of the precursor over the patterned recess of the substrate under first process conditions, said method comprising: (i) supplying the precursor to the reaction space in a manner providing a second partial pressure of the precursor over the patterned recess of the substrate under second process conditions, wherein the second partial pressure is higher than the first partial pressure to the extent providing filling capability to a film when being deposited under the second process conditions; and (ii) exposing the patterned recess of the substrate to a plasma under the second process conditions to deposit a film having filling capability wherein during the entire period of exposing the patterned recess of the substrate to the plasma, a partial pressure of the precursor is kept above the first partial pressure, thereby filling the recess in a bottom-up manner, wherein whenever step (ii) is conducted, step (i) is conducted concurrently or as a prerequisite step. In accordance with exemplary aspects of these embodiments, the film or deposited material comprises silicon or silicon and carbon.

In some embodiments, all gases supplied to the reaction space throughout steps (i) and (ii) are: the precursor, an optional carrier gas, such as N₂, Ar, and/or He, and an optional plasma ignition gas which can be or include Ar, He, N₂, and/or H₂. In some embodiments, the flow rate (slm) of these optional dry gases is 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0, and ranges between any two of the forgoing numbers, in both PEALD-like process and PECVD with continuous or pulsing plasma, also depending on the above-described factors. In some embodiments, Ar and/or He plasma is used for polymerization, while no H is needed; however, H addition (e.g., about 1% to about 40% relative to the total flow of dry gases) may not detrimental to filling properties. Also, neither O₂, Ar, nor N₂ addition (e.g., about 1% to about 40% relative to the total flow of dry gases) may be detrimental to filling properties.

In some embodiments, the first process conditions include a first process temperature, a first process pressure, a first flow rate of the precursor, a first flow rate of carrier gas, and a first flow rate of plasma ignition gas, wherein in step (ii), the second molar concentration is achieved, without changing the first flow rate of the precursor, by lowering the first process temperature to a second process temperature, increasing the first process pressure to a second process pressure, and/or decreasing the first flow rate of carrier gas and/or the first flow rate of plasma ignition gas.

In some embodiments, a precursor includes a Si—C bond. In these cases, the precursor may be constituted by an alkylsilane. Such precursors include, but are not limited to, dimethyldivynylsilane (having a vapor pressure of 13.3 kPa at 20° C.), dimethvlvynllsilane (having a vapor pressure of 440 kPa at 20° C.), and tetramethylsilane (having a vapor pressure of 80 kPa at 20° C.). In some embodiments, the precursor containing a Si—C bond is constituted by an aromatic silane. In some embodiments, a single precursor is used, and alternatively, two or more precursors in combination can also be used. The precursor can have at least one double bond such as a vinyl group for plasma polymerization. Although any suitable precursor (e.g., containing a Si—C bond) can be used as a monomer, such a monomer (e.g., with a Si—C bond) can have a vapor pressure of more than 100 Pa at 25° C., a silicon atom of the monomer bonded to a saturated chain or unsaturated carbon chain, and/or comprise an aromatic compound with or without a halogen substituent. In accordance with further embodiments, the precursor can include one or more organic and/or inorganic silanes, such as one or more of an organosilane, silane, disilane, trisilane, cyclopentasilane, or the like.

In some embodiments, the plasma-assisted deposition is plasma-enhanced CVD deposition, wherein the precursor is continuously supplied to the reaction space throughout steps (i) and (ii). In some embodiments, RF power is applied continuously or cyclically throughout step (ii).

Alternatively, in some embodiments, the plasma-assisted deposition is plasma-enhanced ALD deposition, each ALD cycle of which includes step (i) wherein the precursor is supplied in a pulse, and step (ii) wherein RF power is applied in a pulse without overlapping the pulse of the precursor.

In some embodiments, steps (i) and (ii) continue until the patterned recess is fully filled with the film having filling capability wherein substantially no voids (which can be observed in a STEM photograph of a cross-sectional view of the trench as an empty space having a size of about 5 nm or larger) are formed in the filled recess.

In some embodiments, steps (i) and (ii) are stopped when the film having filling capability is deposited on a bottom and sidewalls of the patterned recess in a shape such that a cross section of the deposited film in the recess has a downward parabola shaped top surface, wherein a thickness of the deposited film in the recess at a center of the bottom of the recess is at least twice that of the deposited film on a top surface of the substrate, and substantially no voids are formed in the filled recess.

In some embodiments, the method further comprises, after completion of the deposition of the film having filling capability, exposing the substrate to a (e.g., hydrogen) plasma as a post-deposition treatment. Periodic H (or O) plasma treatment can be applied with benefits in term of shrinkage after annealing (e.g., at 450° C. for 30 minutes in nitrogen atmosphere), reactive ion (RI), dry etch rate properties, and O content. The effect of the H₂ treatment is to form a higher cross linkage order of the polymer or material, stabilizing the polymer or material structures and properties. O₂ treatment effect, on the other hand, is simply oxidation (e.g., of a polysilane converted to SiO). In some embodiments where a PEALD-like process is conducted, the periodic plasma treatment can be conducted at an RF power (W) of 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 10000, and ranges between any two of the forgoing numbers as measured for a 300-mm wafer which can be converted to units of W/cm² for different sizes of wafers, fora duration (seconds) of 1, 5, 10, 20, 30, 40, 50, 60, and ranges between any two of the forgoing numbers, and at an ALD cycle/treatment ratio of 1/1, 2/1, 3/1, 4/1, 5/1, 6/1, 7/1, 8/1, 9/1, 10/1, 20/1, 30/1, 40/1, 50/1.

In some embodiments, the second process conditions include a second process pressure and a second process temperature wherein the second process temperature is higher than a melting point of the film having filling capability but lower than an ebullition point thereof at the second partial pressure.

The embodiments will be explained with respect to the drawings. However, the present invention is not limited to the drawings.

The continuous flow of the carrier gas can be accomplished using a flow-pass system (FPS) wherein a carrier gas line is provided with a detour line having a precursor reservoir (bottle), and the main line and the detour line are switched, wherein when only a carrier gas is intended to be fed to a reaction chamber, the detour line is closed, whereas when both the carrier gas and a precursor gas are intended to be fed to the reaction chamber, the main line is closed and the carrier gas flows through the detour line and flows out from the bottle together with the precursor gas. In this way, the carrier gas can continuously flow into the reaction chamber and can carry the precursor gas in pulses by switching the main line and the detour line. FIG. 1B illustrates a precursor supply system using a flow-pass system (FPS) according to an embodiment of the present invention (black valves indicate that the valves are closed). As shown in (a) in FIG. 1B, when feeding a precursor to a reaction chamber (not shown), first, a carrier gas such as Ar (or He) flows through a gas line with valves b and c, and then enters a bottle (reservoir) 20. The carrier gas flows out from the bottle 20 while carrying a precursor gas in an amount corresponding to a vapor pressure inside the bottle 20 and flows through a gas line with valves f and e and is then fed to the reaction chamber together with the precursor. In the above, valves a and d are closed. When feeding only the carrier gas (noble gas) to the reaction chamber, as shown in (b) in FIG. 1B, the carrier gas flows through the gas line with the valve a while bypassing the bottle 20. In the above, valves b, c, d, e, and f are closed.

A skilled artisan will appreciate that the apparatus includes one or more controller(s) (not shown) programmed or otherwise configured to cause the deposition and reactor cleaning processes described elsewhere herein to be conducted. The controller(s) are communicated with the various power sources, heating systems, pumps, robotics, and gas flow controllers or valves of the reactor, as will be appreciated by the skilled artisan.

The process cycle can be performed using any suitable apparatus including an apparatus illustrated in FIG. 1A, for example. FIG. 1A is a schematic view of a PEALD apparatus, desirably in conjunction with controls programmed to conduct the sequences described below, usable in some embodiments of the present invention. In this figure, by providing a pair of electrically conductive flat-plate electrodes 4, 2 in parallel and facing each other in the interior 11 (reaction zone) of a reaction chamber 3, applying HRF power (e.g., 13.56 MHz or 27 MHz) from a power source 25 to one side, and electrically grounding the other side 12, a plasma is excited between the electrodes. A temperature regulator is provided in a lower stage 2 (the lower electrode), and a temperature of a substrate 1 placed thereon is kept constant at a given temperature. The upper electrode 4 can serve as a shower plate as well, and reactant gas and/or dilution gas, if any, and precursor gas can be introduced into the reaction chamber 3 through a gas line 21 and a gas line 22, respectively, and through the shower plate 4. Additionally, in the reaction chamber 3, a circular duct 13 with an exhaust line 7 is provided, through which gas in the interior 11 of the reaction chamber 3 is exhausted. Additionally, a transfer chamber 5 disposed below the reaction chamber 3 is provided with a seal gas line 24 to introduce seal gas into the interior 11 of the reaction chamber 3 via the interior 16 (transfer zone) of the transfer chamber 5 wherein a separation plate 14 for separating the reaction zone and the transfer zone is provided (a gate valve through which a wafer is transferred into or from the transfer chamber 5 is omitted from this figure). The transfer chamber is also provided with an exhaust line 6. In some embodiments, the deposition of multi-element film and surface treatment are performed in the same reaction space, so that all the steps can continuously be conducted without exposing the substrate to air or other oxygen-containing atmosphere.

In some embodiments, in the apparatus depicted in FIG. 1A, the system of switching flow of an inactive gas and flow of a precursor gas illustrated in FIG. 1B (described earlier) can be used to introduce the precursor gas in pulses without substantially fluctuating pressure of the reaction chamber.

A skilled artisan will appreciate that the apparatus includes one or more controller(s) (not shown) programmed or otherwise configured to cause the deposition and reactor cleaning processes described elsewhere herein to be conducted. The controller(s) are communicated with the various power sources, heating systems, pumps, robotics and gas flow controllers or valves of the reactor, as will be appreciated by the skilled artisan.

In some embodiments, a dual chamber reactor (two sections or compartments for processing wafers disposed close to each other) can be used, wherein a reactant gas and a noble gas can be supplied through a shared line whereas a precursor gas is supplied through unshared lines.

The film having filling capability can be applied to various semiconductor devices including, but not limited to, cell isolation in 3D cross point memory devices, self-aligned via, dummy gate (replacement of current poly Si), reverse tone patterning, PC RAM isolation, cut hard mask, and DRAM storage node contact (SNC) isolation.

EXAMPLES

In the following examples where conditions and/or structures are not specified, the skilled artisan in the art can readily provide such conditions and/or structures, in view of the present disclosure, as a matter of routine experimentation. A skilled artisan will appreciate that the apparatus used in the examples included one or more controller(s) (not shown) programmed or otherwise configured to cause the deposition and reactor cleaning processes described elsewhere herein to be conducted. The controller(s) were communicated with the various power sources, heating systems, pumps, robotics and gas flow controllers or valves of the reactor, as will be appreciated by the skilled artisan.

Example 1

A Si—C containing film was deposited on a Si substrate (having a diameter of 300 mm and a thickness of 0.7 mm) having narrow trenches with a width of approximately 30 nm and wide trenches with a width of approximately 75 nm, which had a depth of approximately 70 nm, by pure PECVD, pulse feed PECVD, pulse plasma PECVD, or PEALD-like process in order to determine the filling capability of the film, under the conditions shown in Table 5 below using the apparatus illustrated in FIG. 1A and a gas supply system (FPS) illustrated in FIG. 1B. A carrier gas (its flow rate was 0.1 slpm) was used to feed the precursor to the reaction chamber. However, the carrier gas is not required because of the high vapor pressure of the precursor. In this example, small mass flow of the carrier was used just as a precaution against precursor condensation in the line. If the line is sufficiently heated, no carrier gas need be used. Further, although the dry He flow was used to make the plasma ignition easier and more stable, the dry He flow can be eliminated as long as a plasma is ignited. The films were deposited to fully fill the trenches and further accumulate thereon, forming a planar top surface. A cross-sectional view of each substrate with the filled trenches was photographed using STEM.

TABLE 5 (numbers are approximate) gap pressure power Temp feed purge RF-on RF purge dry He gap (mm) (Pa) (W) (° c.) (s) (s) (s) (s) (slpm) fill Pure 15 800 300 74 continuous 0 continuous 0 1.5 yes PECVD Pulse 15 800 300 74 0.1 (1.7 s 0 continuous 0 1.5 no feed interval) PECVD Pulse 15 800 300 74 continuous 0 1 (0.8 s 0 1.5 yes plasma interval) PECVD PEALD- 15 800 300 74 0.1 0.2 1 0.5 1.5 yes like

FIG. 16 shows a STEM photograph of a cross-sectional view of wide and narrow trenches subjected to gap-fill deposition by the pure PECVD. FIG. 17 shows a STEM photograph of a cross-sectional view of wide and narrow trenches subjected to gap-fill deposition by pulse feed PECVD. FIG. 18 shows a STEM photograph of a cross-sectional view of wide and narrow trenches subjected to gap-fill deposition by pulse plasma PECVD. FIG. 10 shows STEM photographs of cross-sectional views of narrow trenches subjected to gap-fill deposition cycles by the PEALD-like process, in which each cycle was repeated 50 times in (a) and 250 times in (c), and wide trenches subjected to gap-fill cycle repeated 50 times in (b) and 250 times in (d). As shown in the STEM photographs, the film deposited by pulse feed PECVD did not have filling capability, and not only the narrow trenches but also the wide trenches showed formation of voids. This is because there was a time period where no precursor was fed while RF power was applied; that is, during the entire period of exposing the patterned recess of the substrate to the plasma, a partial pressure of the precursor was not always kept above a precursor partial pressure required for gap filling. During the time period where no precursor was fed while RF power was applied, plasma polymerization was stopped or material was solidified, degrading the flowability of the material.

FIG. 12 shows Fourier Transform Infrared (FTIR) spectra of the gap-fill layer by the PEALD-like process. As shown in FIG. 12 , the deposited material contained Si—C bonds and C—H bonds, confirming that the material was a SiC-based material.

Example 2

Flowable films were deposited by the PEALD-like process under the conditions used in Example 1 except those shown in Table 6 below, to determine the effect of the type of dry gas and the flow rate thereof with regard to flowability of the depositing films.

TABLE 6 gap pressure power temp feed purge RF-on RF purge dry He N2 O2 H2 Ar (mm) (Pa) (W) (c.) (s) (s) (s) (s) (slpm) (slpm) (slpm) (slpm) (slpm) 15 800 300 74 0.1 0.2 1 0.5 1.5 0 0 0 0 15 800 300 74 0.1 0.2 1 0.5 1.2 0.3 0 0 0 15 800 300 74 0.1 0.2 1 0.5 1.2 0 0.3 0 0 15 800 300 74 0.1 0.2 1 0.5 1.2 0 0 0.3 0 15 800 300 74 0.1 0.2 1 0.5 1.2 0 0 0 0.3

FIG. 19 shows STEM photographs of cross-sectional views of gap filled trenches using, as dry gas, 100% He in (a), 80% He+20% H₂ in (b), 80% He+20% N₂ in (c), 80% He+20% Ar in (d), and 80% He+20% O₂ in (e) according to embodiments of the present invention. In the above, % value is relative to the total of dry gases. As shown in FIG. 19 , Ar or He plasma was used for the polymerization; no H was needed, but H addition was not detrimental to filling capability of the film; also, neither O₂, Ar, nor N₂ addition was detrimental to filling capability. These gases can be used as long as their flow rates are less than 50%, preferably less than 30%, and the majority or predominant portion of the dry gas is He. In some embodiments, none of O₂, Ar, and N₂ is included in the dry gas.

Example 3

A Si—C containing film was deposited on a Si substrate (having a diameter of 300 mm and a thickness of 0.7 mm) having narrow trenches with a width of approximately 30 nm and wide trenches with a width of approximately 75 nm, which had a depth of approximately 70 nm, by PEALD-like process in order to determine the filling capability of the film, under the conditions shown in Table 7 below using the apparatus illustrated in FIG. 1A and a gas supply system (FPS) illustrated in FIG. 1B as in Example 1. The carrier gas (its flow rate was 0.1 slpm) was used to feed the precursor to the reaction chamber as in Example 1. The films were deposited to fully fill the trenches and further accumulate thereon, forming a planar top surface.

TABLE 7 (numbers are approximate) gap pressure power temp feed purge RF-on RF purge dry He No. (mm) (Pa) (W) (c.) (s) (s) (s) (s) (slpm) flowable 1 10 800 50 300 0.1 1.2 0.3 0.1 1.5 no 2 10 200 50 300 0.1 0.2 0.7 0.1 1.5 no 3 10 800 50 300 0.1 0.2 2 0.1 1.5 no 4 10 200 200 300 0.1 0.2 0.3 0.1 1.5 no 5 10 200 50 300 0.1 2 2 0.1 1.5 no 6 10 800 125 300 0.1 2 2 0.1 1.5 no 7 10 500 125 300 0.1 1.2 1.3 0.1 1.5 no 8 10 800 50 300 0.1 2 1.3 0.1 1.5 no 9 10 800 200 300 0.1 2 0.3 0.1 1.5 no 10 10 500 200 300 0.1 2 2 0.1 1.5 no 11 10 200 200 300 0.1 2 1.3 0.1 1.5 no 12 10 200 200 300 0.1 0.2 2 0.1 1.5 no 13 10 800 125 300 0.1 0.2 0.3 0.1 1.5 no 14 10 800 200 300 0.1 1.2 2 0.1 1.5 no 15 10 800 200 300 0.1 0.2 1.3 0.1 1.5 no 16 10 500 50 300 0.1 2 0.3 0.1 1.5 no 17 10 200 125 300 0.1 2 0.3 0.1 1.5 no 18 10 500 200 300 0.1 0.2 0.3 0.1 1.5 no 19 10 800 200 300 0.1 0.2 1.1 0.1 1.5 no 20 10 500 50 300 0.1 0.2 1.1 0.1 1.5 no 21 10 800 200 300 0.1 0.2 2 0.1 1.5 no 22 10 800 50 300 0.1 0.2 2 0.1 1.5 no 23 10 200 50 300 0.1 0.2 0.3 0.1 1.5 no 24 10 200 200 300 0.1 0.2 0.3 0.1 1.5 no 25 10 200 200 300 0.1 0.2 1.1 0.1 1.5 no 26 10 200 50 300 0.1 0.2 2 0.1 1.5 no 27 10 200 200 300 0.1 0.2 2 0.1 1.5 no 28 10 800 200 300 0.1 0.2 0.3 0.1 1.5 no 29 10 800 50 300 0.1 0.2 0.3 0.1 1.5 no 30 10 300 200 300 0.1 0.2 0.7 0.1 1.5 no 31 10 300 200 75 0.5 0.2 2 1 1.5 no 32 15 800 50 300 0.5 0.2 2 0.5 1.5 no 33 15 300 125 300 0.1 0.2 2 1 1.5 no 34 15 300 125 300 0.5 0.2 0.3 0.1 1.5 no 35 13 800 200 75 0.5 0.2 0.3 0.6 1.5 yes 36 10 500 200 75 0.1 0.2 0.3 0.1 1.5 no 37 15 800 50 75 0.1 0.2 0.3 1 1.5 yes 38 12 600 50 75 0.5 0.2 2 0.1 1.5 no 39 10 300 50 75 0.5 0.2 0.3 0.7 1.5 no 40 10 300 200 300 0.3 0.2 2 0.1 1.5 no 41 10 800 50 300 0.2 0.2 0.3 1 1.5 no 42 15 800 50 75 0.5 0.2 0.6 1 1.5 yes 43 15 800 300 75 0.5 0.2 0.9 0.1 1.5 yes 44 15 800 300 75 0.1 0.2 0.9 0.1 1.5 yes 45 15 800 300 75 0.1 0.2 0.9 0.1 1.5 yes 46 15 800 300 75 0.1 0.2 0.9 0.1 1.5 yes 47 15 800 300 75 0.1 0.2 1 0.5 1.5 yes 48 15 1100 300 85 0.1 0.2 1 0.5 0.5 yes 49 15 1100 300 85 0.1 0.2 1 0.5 1 yes 50 15 1100 300 85 0.1 0.2 1 0.5 1.5 yes 51 15 800 300 85 0.1 0.2 1 0.5 1.5 yes 52 15 500 300 85 0.1 0.2 1 0.5 0.5 yes 53 15 500 300 85 0.1 0.2 1 0.5 1.305 no 34 15 1100 300 120 0.1 0.2 1 0.5 0.5 yes 55 15 1100 300 120 0.1 0.2 1 0.5 1.5 yes 56 15 800 300 120 0.1 0.2 1 0.5 1 yes 57 15 500 300 120 0.1 0.2 1 0.5 0.5 yes 58 15 500 300 120 0.1 0.2 1 0.5 1.5 no 59 13 1000 500 35 0.1 0.3 0.8 0.5 0 yes 60 13 1000 300 35 0.1 0.3 2 0.5 0.6 yes 61 17 500 500 35 0.1 0.3 2 0.5 0.6 yes 62 13 500 300 75 0.1 0.1 0.8 0.5 0 yes 63 13 500 300 75 0.1 0.3 0.8 0.5 0.6 no 64 13 500 500 75 0.1 0.1 2 0.5 0.6 no 65 17 1000 300 75 0.1 0.3 2 0.5 0 yes 66 17 1000 500 75 0.1 0.1 0.8 0.5 0 yes 67 17 750 300 75 0.1 0.1 2 0.5 0.6 yes 68 17 1000 500 75 0.1 0.3 1.4 0.5 0.6 yes 69 13 850 200 50 0.1 0.2 1.25 0.5 1.5 yes 70 13 600 400 50 0.1 0.2 1.25 0 1.5 yes 71 13 1000 200 50 0.1 0.2 2 0 1 yes 72 13 600 200 50 0.1 0.2 0.5 0 1.5 no 73 13 1000 400 50 0.1 0.2 2 1 1.5 no 74 17 1000 400 50 0.1 0.2 2 1 0.5 yes 75 17 600 200 50 0.1 0.2 1.25 1 0.5 yes 76 17 1000 400 50 0.1 0.2 1.25 0 1 yes 77 17 600 400 50 0.1 0.2 0.5 1 0.5 no 78 13 750 400 100 0.1 0.2 0.5 0 1 no 79 13 600 400 100 0.1 0.2 2 1 0.5 no 80 13 1000 400 100 0.1 0.2 1.25 1 0.5 no 81 13 1000 200 100 0.1 0.2 0.5 0 0.5 no 82 13 600 200 100 0.1 0.2 1.25 1 0.5 no 83 17 850 200 100 0.1 0.2 2 0 0.5 no 84 17 600 200 100 0.1 0.2 2 0 1.5 no 85 17 600 400 100 0.1 0.2 1.25 1 1.5 yes 86 17 1000 400 100 0.1 0.2 0.5 1 1.5 yes 87 13 1000 200 50 0.1 0.2 2 0 1.5 yes 88 13 1000 200 35 0.1 0.2 2 0 1.5 yes 89 13 1000 200 35 0.1 0.2 2 0 1.8 no 90 14.8 1200 242 50 0.1 0.2 2 0 1.4 yes 91 17 700 400 50 0.1 0.2 1.4 0 1.5 yes 92 17 1000 400 50 0.1 0.2 1.4 0 1.5 yes 93 16.2 1000 370 50 0.1 0.2 2 0 1.5 yes 94 16.2 1000 370 50 0.1 0.2 1.4 0 1.5 yes 95 16.2 1000 300 50 0.1 0.2 1.4 0 1.5 yes 96 17 500 400 50 0.1 0.2 1.5 0 0.5 yes 97 17 500 400 100 0.1 0.2 0.8 1 1.5 yes 98 13.5 1000 200 50 0.1 0.2 1.3 0 1.5 yes 99 14 950 150 60 0.1 0.2 1.6 0 1.3 yes 100 15 850 130 70 0.1 0.2 1.4 0 1.2 yes 101 12 1050 150 40 0.1 0.2 2.2 0 1.7 yes 102 12 950 250 40 0.1 0.2 1.8 0 1.3 yes 103 12 1050 150 40 0.1 0.2 2.2 0 1.3 yes 104 14 1050 150 40 0.1 0.2 1.8 0 1.7 yes 105 14 950 250 40 0.1 0.2 2.2 0 1.7 yes 106 12 950 150 60 0.1 0.2 1.8 0 1.7 yes 107 12 1050 250 60 0.1 0.2 2.2 0 1.7 yes 108 14 1050 250 60 0.1 0.2 1.8 0 1.3 yes 109 14 950 150 60 0.1 0.2 2.2 0 1.3 yes 110 14 1050 150 60 0.1 0.2 2.2 0 1.3 yes 111 17 350 130 75 0.1 0.2 1.5 0.3 0.6 yes 112 10 1090 550 113 0.1 0.2 0.6 1 1.8 yes 113 18 520 130 35 0.1 0.2 2 0 0.6 yes 114 18 520 130 35 0.1 0.2 2 1 0.6 yes 115 12 800 100 35 0.1 0.2 2.3 0 1 yes 116 16 600 600 150 0.1 0.2 3 0 0.1 no 117 16 1100 100 150 0.1 0.2 3 0 0.1 no 118 16 1100 350 150 0.1 0.2 0.5 0 1 no 119 10 600 600 225 0.1 0.2 3 0 1 no 120 10 1100 100 225 0.1 0.2 3 0 1 no 121 13 600 350 225 0.1 0.2 0.5 0 0.1 no 122 16 600 600 225 0.1 0.2 0.5 0 1 no 123 16 1100 100 225 0.1 0.2 1.75 0 0.55 no 124 10 600 350 300 0.1 0.2 1.75 0 1 no 125 10 600 600 300 0.1 0.2 0.5 0 0.1 no 126 10 1100 100 300 0.1 0.2 0.5 0 0.1 no 127 10 1100 600 300 0.1 0.2 0.5 0 1 no 128 10 1100 600 300 0.1 0.2 3 0 0.1 no 129 13 600 100 300 0.1 0.2 3 0 0.55 no 130 16 600 100 300 0.1 0.2 0.5 0 1 no 131 16 600 100 300 0.1 0.2 3 0 0.1 no 132 16 1100 600 300 0.1 0.2 0.5 0 0.1 no 133 16 1100 600 300 0.1 0.2 3 0 1 no 134 16 800 600 150 0.1 0.2 3 0 0.1 no 135 16 1100 350 150 0.1 0.2 3 0 1 no 136 16 600 600 150 0.1 0.2 3 0 0.1 no 137 10 1100 100 150 0.1 0.2 3 0 0.1 no 138 10 1100 350 225 0.1 0.2 0.5 0 1 no 139 13 600 600 225 0.1 0.2 3 0 1 no 140 16 1100 100 225 0.1 0.2 3 0 1 no

As discussed later, the effect of precursor depletion during a long RF-on period and a problem with activation due to a too short RF-on period influence gap fill capability. Also, the phase change may be a critical aspect for gap fill capability.

In the above, between #57 and #58, since the dry He flow increased in #58, the precursor partial pressure at the deposition temperature (the “modified factor”) decreased (fewer molecules in the space), thereby rendering the film incapable of gap filling; however, although the process conditions in #82 and #85 were not significantly different from those in #57 and #58, even though the dry He flow increased in #85, i.e., the modified factor decreased, the film had gap fill capability (this result was directly opposite to that in #58). This appears to be because in #85, the gap was greater than in #82, thereby increasing the modified factor (more molecules in the space). However, considering the degree of difference in “dry He” between #82 and #85, the difference in “gap” between #82 and #85 was not as significant as that in “dry He.” Similar phenomena are observed in #81 and #86. It appears that the difference between #82 and #85 resides in the difference in “RF-on,” i.e., in #82, RF power application was so long that the precursor was used up by the end of RF power application, interfering with gap filling. This phenomenon was observed in #84 and #85. As previously discussed, while RF was on, the gas phase appeared to be rapidly depleting and the partial pressure of precursor appeared to become insufficient for polymerization. And regarding the comparison pair #81 and #86, in both cases the RF-on period was very short but #82 did not show flowability while #87 did. The power was 200 W in case of #82 and 400 W in case of #87. It appears that because in #82, the RF-on period was short and RF power was low, energy was insufficient for polymerization.

When RF power application was too short to cause polymerization, then, the film was not gap fill-capable. This phenomenon was observed in #70 and #72, and #75 and #77. However, between #62 and #63, it appeared that in #63, “dry He” increased to 0.6, and thus, the partial pressure of precursor decreased, and this was the reason for non-gap fill. However, when in #35, “dry He” increased further to 1.5, and the partial pressure of precursor further decreased, the film had gap filling capability. It appears that in #36, the feed time was 0.5 sec, which was 5 times longer than #62 and #63, for example, resulting in a much higher dose of precursor, i.e., higher precursor partial pressure.

In gap filling processes, the depositing material desirably remains viscous or liquid and should not solidify or evaporate. The vapor pressure of the liquid phase (not the precursor) should be lower than the total pressure. Analogy to the above can be observed in the case of, for example, water, where water boils at 100° C. under 760 mmHg, and at about 60° C. under 200 mmHg, regardless of the partial pressure. Thus, temperature and pressure should be such that the liquid phase is below a boiling point and above a melting point of the depositing material.

In view of the above and the entire disclosure, by designating process conditions where a film without filling capability is depositable as a reference film on the substrate as first process conditions (including a first partial pressure of the precursor at a deposition temperature), a skilled artisan in the art can readily set a second partial pressure of the precursor at a deposition temperature through routine experimentation wherein the second partial pressure is higher than the first partial pressure to the extent providing filling capability to a film when being deposited under second process conditions.

Example 4

Flowable films were deposited by the PEALD-like process under the conditions used in Example 1 except that (a) the substrate had trenches having a higher aspect rate (an aspect ratio was approximately 10) than in Example 1 (an aspect ratio was approximately 10), and (b) the film was deposited on a SiO layer. As a results, STEM photographs of cross-sectional views of the gap-filled wide trenches in (a) and the gap-filled deep, narrow trenches in (b) confirmed that each film had excellent filling capability.

Example 5

Flowable films were deposited by the PEALD-like process under the conditions used in Example 1. Thereafter, periodic H plasma treatment was conducted under the conditions shown in Table 8 below to provide some benefits in terms of shrinkage after anneal (30 minutes at 450° C. in N₂ atmosphere), RI, and dry etch rate properties, which are also shown in Table 8.

TABLE 8 H2 cross linking cycle/treatment treatment treatment DER Shrinkage Film ratio time (s) power (W) RI (standardize) by anneal (%) New No treatment 1.54 4 68 SiC 4 30 100 1.58 3 0.7 GF 4 30 300 1.61 2.7 2.4 4 180 100 2.04 0.95 0

FIG. 13 shows STEM photographs of cross-sectional views of gap-filled wide trenches subjected to the periodic hydrogen plasma treatment in (a), and gap-filled narrow trenches subjected to the periodic hydrogen plasma treatment in (b). As shown in FIG. 13 , by conducting the periodic hydrogen plasma treatment, substantially no shrinkage of the deposited material upon annealing was observed.

Example 6

A flowable films was deposited by the PEALD-like process in a manner similar to that in Example 5. Thereafter, periodic H plasma treatment was conducted in a manner similar to that in Example 5 to provide some benefices in term of RI and dry etch rate properties, and O content, which are also shown in Table 9.

TABLE 9 Composition Si C H O N RI Dry etch rate Without H₂ 20 28 44 8 0 1.52 3.1 plasma With H₂ plasma 21 49 30 0 0 2.02 2 (200 W)

It will be understood by those of skill in the art that numerous and various modifications can be made without departing from the spirit of the present invention. Therefore, it should be clearly understood that the forms of the present invention are illustrative only and are not intended to limit the scope of the present invention. 

1. A method for filling a patterned recess of a substrate by plasma-assisted deposition of a film having filling capability using a precursor in a reaction space, where a film without filling capability is depositable as a reference film on the substrate using the precursor in the reaction space when the precursor is supplied to the reaction space in a manner providing a first partial pressure of the precursor over the patterned recess of the substrate under first process conditions, said method comprising: (i) supplying the precursor to the reaction space in a manner providing a second partial pressure of the precursor over the patterned recess of the substrate under second process conditions, wherein the second partial pressure is higher than the first partial pressure to the extent of providing filling capability to the film when being deposited under the second process conditions; and (ii) exposing the patterned recess of the substrate to a plasma under the second process conditions to deposit the film having filling capability, wherein during the period of exposing the patterned recess of the substrate to the plasma, a partial pressure of the precursor is kept above the first partial pressure, thereby filling the recess in a bottom-up manner, wherein whenever step (ii) is conducted, step (i) is conducted concurrently or as a preceding step.
 2. The method according to claim 1, wherein all gases supplied to the reaction space throughout steps (i) and (ii) are: the precursor, an optional carrier and an optional plasma ignition gas.
 3. The method according to claim 1, wherein the first process conditions include a first process temperature, a first process pressure, a first flow rate of the precursor, a first flow rate of carrier gas, and a first flow rate of plasma ignition gas, wherein in step (ii), the second molar concentration is achieved, without changing the first flow rate of the precursor, by lowering the first process temperature to a second process temperature, increasing the first process pressure to a second process pressure, and/or decreasing the first flow rate of carrier gas and/or the first flow rate of plasma ignition gas.
 4. The method according to claim 1, wherein the precursor is constituted by an alkylsilane.
 5. The method according to claim 1, wherein the precursor is constituted by an aromatic silane.
 6. The method according to claim 1, wherein the plasma-assisted deposition is plasma-enhanced CVD deposition, wherein the precursor is continuously supplied to the reaction space throughout steps (i) and (ii).
 7. The method according to claim 6, wherein RF power is applied continuously or cyclically throughout step (ii).
 8. The method according to claim 1, wherein the plasma-assisted deposition is plasma-enhanced ALD deposition, each ALD cycle of which includes step (i) wherein the precursor is supplied in a pulse, and step (ii) wherein RF power is applied in a pulse without overlapping the pulse of the precursor.
 9. The method according to claim 1, wherein steps (i) and (ii) continue until the patterned recess is fully filled with the film having filling capability wherein substantially no voids are formed in the filled recess.
 10. The method according to claim 1, wherein steps (i) and (ii) are stopped when the film having filling capability is deposited on a bottom and sidewalls of the patterned recess in a shape such that a cross section of the deposited film in the recess has a downward parabola-shaped top surface wherein a thickness of the deposited film in the recess at a center of the bottom of the recess is at least twice that of the deposited film on a top surface of the substrate, and substantially no voids are formed in the filled recess.
 11. The method according to claim 1, further comprising, after completion of the deposition of the film having filling capability, exposing the substrate to a hydrogen plasma as a post-deposition treatment.
 12. The method according to claim 1, wherein the second process conditions include a second process pressure and a second process temperature wherein the second process temperature is higher than a melting point of the film having filling capability but lower than an ebullition point thereof at the second partial pressure. 